The present invention relates generally to actuators for valves, and more particularly to control systems for such actuators.
The present invention comprises an actuator system for a system valve exposable to a source of system pressure. The system includes a sensing assembly, formed from a sensing vessel having a tubular internal cavity and a piston assembly. The piston assembly comprises a piston positioned within the internal cavity, the piston having at least a first position and a second position. The second position of the piston is longitudinally offset from the first position in a second direction. The piston assembly further comprises a piston control system adapted to move the piston from its first position to its second position in response to a designated system pressure.
The system further comprises an actuator, adapted for engagement with the system valve. The actuator has an unactuated state and an actuated state, and is adapted to shift from the unactuated state to the actuated state in response to a predetermined change in pressure at the actuator. The actuator is interconnectable with an actuator pressure source by an actuator fluid path.
An actuator control valve is interposed in the actuator fluid path. The actuator control valve is coupled to the piston, and produces the predetermined change in pressure at the actuator in response to movement of the piston from its first to its second position.